A research project has been undertaken with the aim of developing wood-based cellulosic thermal insulation panel material manufactured by foam forming with high performance and to explore the possibilities of creating a new bio-based cellulosic in-situ spray-on thermal insulation foam to replace traditional spray-on plastics insulation foams. Insulation boards were manufactured from 100% softwood and a mixture of softwood and microfibrillated cellulose (MFC). The foaming surfactant used was sodium dodecyl sulphate (SDS). The materials made of softwood and MFC mixtures were made by layering. The thermal conductivity behaviour of the boards was investigated. It has been demonstrated that by using foam forming technology, nanofibrillated cellulose and softwood kraft pulp, it was possible to create high bulk fibre networks with good thermal insulation properties that simultaneously had outstanding high air flow resistivity in relation to the total density of the material. The results obtained were affected by board density. Air flow decreased with board bulk density, due to higher tortuosity of fibrous structure. Air flow resistance increased with layering strategy, with MFC layer enhancing the performance of boards to limit air going across the board.